In U.S. Provisional Patent Applications Nos. 61/107,112 filed Oct. 21, 2008, 61/193,457 filed Dec. 2, 2008, 61/202,070 filed Jan. 26, 2009, 61/202,553 filed Mar. 12, 2009, 61/213,717 filed Jul. 7, 2009, 61/272,241 filed Sep. 3, 2009, and U.S. patent application Ser. No. 12/603,087 filed Oct. 21, 2009 the disclosures of which are incorporated herein by reference, there is described the preparation of a soy protein product, preferably a soy protein isolate, which is completely soluble and is capable of providing transparent and heat stable solutions at low pH values. This soy protein product may be used for protein fortification of, in particular, soft drinks and sports drinks, as well as other acidic aqueous systems, without precipitation of protein. The soy protein product is produced by extracting a soy protein source with aqueous calcium chloride solution at natural pH, optionally diluting the resulting aqueous soy protein solution, adjusting the pH of the aqueous soy protein solution to a pH of about 1.5 to about 4.4, preferably about 2.0 to about 4.0, to produce an acidified clear soy protein solution, which may be optionally concentrated and/or diafiltered before drying.